Current documentation for Oauth for CN is as follows the urls should be
www.battlenet.com.cn/oauth/authorize
www.battlenet.com.cn/oauth/tokentry these and you should get a better result
No, those URLs are severely outdated (and haven’t worked for many years). The “Using OAuth” documentation at (https://develop.battle.net/documentation/guides/using-oauth) states https://oauth.battlenet.com.cn/authorize. This changed back in late 2018 when the URLs migrated:
https://<region>.battle.net/oauth/→https://oauth.battle.net/https://www.battlenet.com.cn/oauth/→https://oauth.battlenet.com.cn/)
I’d link to the dev portal announcement, but Blizzard hasn’t kept the migration announcement around (was formerly at https://develop.battle.net/documentation/guides/migration-guide).
I suspect you got this from the “Battle.net OAuth APIs – CN” documentation (at https://develop.battle.net/documentation/battle-net/oauth-apis-cn) that simply has never been updated. In any case, those old URLs have not worked for many years.
The problem isn’t that the URLs are wrong, it’s that they work and respond as you’d expect, but they don’t seem to recognize the non-CN OAuth clients.